Spark plug



Dec. l0, 1929. H. RAaEzzANA v SPARK PLUG l Filed oct. 2v. 1922 Snoetoi l 1 gmgmm Patented Dec. 1'0, '1929- UNITED STATES PATENT `orfFI'ciE;

HECTOR RABEZZAN'A, OF vIliLIN'JJ, MICHIGAN,. ASSIGNOR TO A. C SPARK.- PLUG COM- PANY, OFFLINT, MICHIGAN, `A..CORPORATION OF MICHIGAN SPARK PLUG Application led October 27, 1922. Serial No. 597,327.

My invention relates to spark plugs designed for use with internal combustion engines to ignite the combustible mixture supplied to the cylinder thereof; andthe principal object of my invention is to provide a construction of spark plugs in which the heat to which the same is subjected -r(which is due in part to the heating action ofthe l j burning mixture within the cylinder and in part to the action of the sparks passing between the terminalsof the plug) is conducted away, from the plug more effectively than has heretoforek commonly been the case, thus maintaining the insulating member of the plug at as low a temperature as possible and '.'avolding injury thereof which would be likel to follow the heating of the same to .an a normally highvtemperature.

Heretofore spark plugs have commonly in cluded an exterior shell or' casing threaded throughout la portion of its length and adapt-A ed to be screwed into a threaded opening in wall; which iiow must as a matterv of coursen a cylinder to thereby fasten the plug in place. In such plugs, however, there is commonly a considerable portion of the shell `which is not in contact at all with the cylinder wall and the joint between the parts, which is made up of the threaded portion of the shell and of the opening in which it is screwed, is a joint not well adapted to facllitate the flow of heat from the plug casing to the'cylinder occur before the heat can be dissipated throughout the` mass of lthe cylinder and to the water acket thereof. My invention obviates this difficulty by very` materially increasing the extent of contact between the opening in the cylinder wall yand the external` metallic shell or casing of the plug and by making a better and more closely fitting .joint between the parts; thus on the one hand providing a joint of very materially increased cross section or area,l and on the other hand providing a joint in which the parts are in more close and intimate Contact with one another than is the case when the plug isf." screwed into a threaded vopening in thegen gine cylinder. Afurther object of my inventionfis `to pro- 'vide an improved spark plug'which may be more readily put in place and removed from the cylinder than has heretofore commonly been the case; and a still further object is to provide a'n improved spark plug which may i be' more readily and cheaply manufactured, and which will be more effective for the purpose for which it is provided, than has heretofore commonly been thecase.

The drawing accompanying and forming a part of this specification illustrates the preferred embodiment of my invention; although it will be appreciated. that the same may take various other forms than the form illustrated, and that my invention includes such variations and modifications of the particular embodiment thereof illustrated as come `within the scope .of the concluding claims.

Referring now to the drawing: Figure l is a view of the upper portion of an. internal combustion engine cylinder having my improvedspark plug fastened in place in the head thereof.

FigureV Z'is a fragmentary vierA upon'a considerably larger scale showing my invention in section, and in placewithin an opening in the cylinder head.

Figure 3 is av view similar to Figure 2-as regards subject matter and scale, but showing a modifiedform of my invention. In the drawing, the reference numeral 5 designates an internal combustion engine cyl- Figurel)l is secured; the plug being fastened inplace in the opening in any way, as, for xam-ple, by the use of a bifurcated yoke one end of which straddles the plug and the other end of which bears against the cylinder wall as an abutment; the yoke being held in place ool relative to the cylinder by means of a stud by itself in Figure 2 ofthe drawing.

bolt 11 and nut 12 upon the free end thereof.

My improved spark plug is best shoTiylnA e same comprises an external metallic sleeve' or casing 13 the periphery of which is tapered to fit the tapered hole provided within the engine cylinder. Within this hollow sleeve or casing an insulating member 14 1s secured, said member being illustrated as of a common and conventional form having lower and upper shoulders 15 and 16. The sleeve 13 is provided with an inwardly turned holding flange 17 which overlies the upper shoulder 16 and holds the insulator permanently-within the shell; suitable gasketsl as shown being commonly interposed between the shoulders and the adjacent surfaces of the sleeve. The holding flange 17 is integral withthe sleeve and is formed from a flange at the upper end thereof which is turned inward and into permanent holding engagement with the insulating member 15 in accordance with the usual practice in making single piecev spark plugs. The insulating member 14 carries the usual central electrode 18 of the plug, while the outer or grounded electrode 19 is carried by the shell or sleeve 13, as is usual in spark plugs.

The joint between the sleeve 13 and the opening) inthe cylinder wall in which itiits should e made in sucha manner as to secure the best possible and the most intimate contact between the surfaces engaging one al1- other, in order to provide fora free fiow of heat from the sleeve 13 outward and into the cylinder wall to thereby dissipate the heat from the insulating member as rapidly as possible and keep its temperatureas low as practicable. This intimacy of contact between the parts may be secured in various ways by lapping or grinding the bushing in place within the opening provided for its reception, whereby contact is secured throughout the entire peripheral surface of the sleeve and the adjacent inner wall of the opening. As an alternative scheme the peripheral surface of the bushing may be electroplated with copper or other suitable soft metal, as indi-- cated at 20; or a thin conical bushing of soft metal may be interposed between the parts; the packin metal or gasket in either case being of suc softness that it will flow slightly under pressure as the plug is fastened in place and thus ll up al1 interstices between the casing and the adjacent surface of the cylinder wall. As a further alternative plan for securing an intimate joint between the parts the meeting surfaces of the sleeve and the cylinder wall, or one of them, may be coated with a` mercury amalgam which, when the casing is forced into place, will provide a most intimate contact between the parts.v

From the foregoing it will be appreciated that in all cases the principal end and aim is to provide a joint between the comparatively massive plug casing 13 and the adjacent cylinder wall which will be of as great area as possible, and which will be of such a character 'as to offer as little resistance as possible to thel iiow o f heat across the joint in question. This provides for a more rapid dissipation of heat from the plug and into the cylinder wall than has heretofore commonly been secured; the result being that the insulating member of the plug remains at a much lower temperature thanvwould be the case if the joint between the plug and the cylinder was of such a character as to impede the fiow of heat from the plug.

. In the modified form of my invention shown inFigure 3 the plug- 9 fits within an external sleeve 21 in precisely the same manner as hereinbefore explained, the sleeve, however, being a member which is separate from the cylinderwall. In this form of my invention the threaded connection between the sleeve and the cylinder wall will as a matter of course ofer more resistance to the flow of heat than a continuous mass of metal, but on the other hand this sleeve may be made of a metal having properties such that a more intimate contact maybe provided between it and the casing 13 of the plug than between said casing and the cast metal from which cylinders are commonly made. It therefore follows that what may be lost by the threaded joint will be gained by the possibility of securing more intimate contact between the plug casing and the sleeve and,v

inasmuch as the sleeve remains permanently in place in the cylinder wall, it may be made of such size as to screw into the threaded opening provided for it with extreme tightness, thus providing a joint in which the parts are in much more intimate contact than is lOl the case in an ordinary 'threaded joint or connection.

Itv will be appreciated that in both and other equivalent forms of my invention the casing of the plug ts within the conical openino' provided for its reception throughout su stantially the entire length of the casing, thus providing a joint of much greater area between the cylinder wall and the casing than heat outward rom the plug is reduced to a minimum; while the s ecifc character of the meeting surfaces at t e joint whereby intimacy of contact above'that heretofore attained is secured, further contributes to the objects to be attained bv m invention.

Having thus described an explained my invention, I claim and desire to 'secure by Letters Patent:

1. In combination withy a cylinder wall having a tapered opening therein, and the wall of which opening is smooth througho ut substantially its entire extent; a smooth and unthreaded metallic shell or casing tapered in form to correspond with said opening, and the length of which is as great as the length of said opening; a yoke member one end of which engages said shell, and the other end of which engages a fixed abutment; a bolt intermediate the ends of said yoke for forcing it against said shell, to thereby secure said shell in place within said opening; an insulating member secured in I place Within said shell; and electrodes carried one by said insulating member and the other by said shell or casing.

2. In combina-tion with a cylinder wall having a tapered-openingv therein and the periphery of which opening is smooth throughout its entire extent; a hollow, smooth and unthreaded metallic shell or casing coni-` cal in form and fitting Within said opening; a yoke engaging the upper end of said shell to hold it in place within said opening; and an insulating member located Within said shell or casing; said shell having a holding flange integral with the upper endv thereof and turned inward and into permanent holding engagement with said insulator; and the peripheral surface of said shell having a metallic coating thereon.

3. In combination with a cylinder Wall having a tapered opening therein; a hollow metallic shell or casing tapering in form and fitting Within said opening, the cooperating surfaces ofsaid shell and the interior of said opening being smooth throughout their entire' extent, and the shell being as lon as `the opening so as to fit therein throug out .the entire extent of the inner peripheral wall thereof; means for holding said shell in place within said opening; an insulating member held in place within said shell or casing; and a thin film of metal upon the exterior peripheral surface of. said shell throughout the area of Contact between the same Vand the inner peripheral Wall of said opening.

4. A spark plug comprising a hollow metallic shell or casing tapering in form and smoothv throughout its conical part, and which casing has an electrode at its inner end, and an inturned holding ilange formed integrally threwith at its upper end; anv insulating member permanently held in place in said shell by the holding fian e aforev said; and an electrode carried by sai insulating member and arranged in sparking relation to said first mentioned electrode.

In testimony whereof I aiiix my signature.

HECTOR RABEZZANA. 

